1. Field of the Invention
The present invention relates to a motion tracking device for use on human skin, and adapted to plot the location of a medical device on a computer monitor, or a topographical map of human tissue.
2. Description of the Prior Art
Presently a large number of medical procedures are done by hand relying solely on the experience and expertise of a physician. Procedures occur every day from the drawing of blood, to the insertion of catheters, or from diagnostic ultrasound scans for imaging a patient, to therapeutic procedures to destroy unwanted tissue. All of these historically rely on the experience and judgment of the physician based on tissue and organs the physician cannot see, but can generally gauge the general position of those tissues.
Few technologies exist at present for a physician to accurately map the surface area of a patient's epidermis, or correlate the surface map with a detailed three dimensional map of the tissue beneath the skin. Further complicating the matter is the need for the physician to have access to the skin or surface area the physician may wish to produce a map of. The necessity of being able to perform a medical procedure at a particular location precludes the utility of a device that accurately measures either surface movement and features, but makes imaging below the surface virtually impossible.
U.S. Pat. No. 4,137,777 to Haverl et al., provides for an apparatus for dynamic focusing and multiple plane scaling of ultrasound to provide repeatability of scan results by removing some level of operator placement of the transducer. However this apparatus does not correlate the image data with a surface map of the patient's skin. Primarily because the apparatus is designed to image organ tissue within the body cavity, and subject to internal movement.
U.S. Pat. No. 5,404,387 to Hammond et al., provides for a system and method for scanning the human body using X-radiation. The device being designed primarily to scan for foreign objects on or in a person. The device converts X-radiation into a video image for display. However this invention does not deal with tracking a medical device on a person nor assist a physician in carrying out a medical procedure. Position tracking on a patient's skin is not provided for here either.
However, position tracking devices are well known in the field of computer science. Nearly every personal computer utilizes some form of “mouse” for position tracking of a cursor on a display screen. The development of computer mouse technology has seen an explosion of different tracking devices. Mechanical mice use a roller-ball mounted within a cell and having multiple roller axes that roll counter to the direction of the track ball in the way of a toothless gear. The mechanism calculates the motion of a track ball and converts that motion into a direction and speed indicator on a screen. The visual display shows a cursor, in the form of an arrow, I-beam or other icon.
Optical mice work by image correlation based on the surface they are tracking over. Early optical mice required light reflecting grids or other special surfaces in order for them to accurately track direction and speed of movement. More recent computer mice allow for digitizing an image of the surface they are moving over and comparing sequential images to determine the change in position. The change in position information is usually processed by an on-board microprocessor that provides a computer with both speed and direction information.
For example, the optical tracking elements of an optical mouse include a small light emitting diode (LED) and a detector functioning as a small camera capable of taking a high number of pictures every second. Camera operations can be performed by a complimentary metal-oxide semiconductor (CMOS) and sends each image to a digital signal processor (DSP). The DSP can be on board or in a separate computer. The DSP can compare sequential images based on an internal clock, or using the DSP's internal clock and compare how images have moved from one frame to the next. This allows the DSP to determine both direction and speed of movement of an optical mouse. There are numerous ways optical mice are constructed and designed to provide pointer/cursor information for a user on a computer screen, the above description is merely illustrative of a generic computer mouse.
A feature optical and mechanical mice share is the ability to track frame to frame or roller movement to roller movement. In essence, the relative location of the mouse is not important so long as the device can track over the surface it is moving on. In this manner a user is able to pick up a mouse when it runs off the edge of a mouse pad, or the user runs out of room, and then replace the mouse on the surface and resume tracking the cursor on the monitor. The cursor on the monitor does not move during the replacing of the mouse, so the cursor position is never lost on the screen.
U.S. Pat. No. 6,618,038 to Bohn, provides for a computer pointing device having two optical encoders, allowing the computer mouse to track both position and orientation changes on a video monitor. However the pointing device is designed for use with a computer system to serve as a pointing device, and not as a position tracking device.
The use of optical sensors and mechanical sensors as pointing devices does not address the issue of an accurate position tracking device. The distinction is made in that the pointing device tracks the position of a cursor in a virtual environment, while a position tracking device tracks a physical position on a surface without concern for any virtual positioning or location. Thus while computer mice can be adjusted for slow or fast tracking over a surface set to a users preference, a position tracking device must be a true representation of actual speed and movement over a surface. The use of a position tracking device can be of great assistance in the medical arts.
Thus there remains a need in the field of medical procedures for a precise position tracking device utilizing reliable sensor technology.
There is further a need for a position tracking device that can be used in tandem with a medical device.
There is still further a need for a position tracking device that can accurately position radiant therapy treatments in a three dimensional environment.
There is still further a need for a position tracking device that can operate in conjunction with a medical device controller or a therapy procedure program to coordinate effective dosing in a two or three dimensional environment without relying on discretionary input from a user.